Manually operated percussion units or rammers are frequently employed to compact soil or other material. A rammer is particularly adapted for use in narrow trenches which, in some instances, can be several feet deep.
A conventional rammer includes a gear case or frame having a handle to be grasped by the operator and a percussion unit is suspended from the gear case. The percussion unit is composed of a reciprocating ram which is held in a neutral position by two pair of opposed compression springs enclosed in a tube. The lower end of the tube carries a shoe which is adapted to engage the soil while the upper end of the ram is connected through a connecting rod and gear drive to the output shaft of a gasoline engine that is mounted on the gear case. With this construction, operation of the engine will reciprocate the ram and tube to compact the soil.
The conventional rammer, as used in the past, has been powered by a two-cycle gasoline engine and if the rammer is used in an enclosed environment, the atmosphere can be readily polluted by the exhaust gas from the engine. Similarly, if the rammer is used in a relatively deep trench, the exhaust fumes can pollute the trench causing a hazard to the operator.
As the rammer is normally operated in dusty conditions, it is necessary to frequently clean the air cleaner of the gasoline engine and due to the dusty conditions of operation, the conventional rammer is subject to high maintenance and repair cost.